Fuel injection system

ABSTRACT

A fuel injection system for internal combustion engines includes a fuel injector that includes a spray-orifice plate through which fuel is injected into a combustion chamber. The combustion chamber is bounded by a cylinder wall. A piston is guided in the cylinder wall, and a spark plug projects into the combustion chamber. The diameters of injection orifices positioned on the spray-orifice disk are distributed such that, at a particular point of injection, the injected fuel is distributed as homogenously as possible in an injection volume of the combustion chamber, bounded by the piston and the cylinder wall.

FIELD OF THE INVENTION

The present invention relates to a fuel injection system.

BACKGROUND INFORMATION

A method for forming an ignitable fuel/air mixture is discussed inGerman Patent No. 196 42 653. An ignitable fuel/air mixture may beformed in the cylinders of internal combustion engines having directinjection in that fuel is injected by an injector into each combustionchamber bounded by a piston, in response to the release of a nozzleorifice as the result of a valve member lifting off from a valve seatthat encircles the nozzle orifice. To produce an internal mixtureformation that is optimized with respect to consumption and emissions,in every operating point of the entire characteristics map, under alloperating conditions of the internal combustion engine, e.g., instratified operation, the opening stroke (lift) of the valve member andthe injection time are variably adjustable.

German Published Patent Application No. 38 08 635 discusses a fuelinjection device for the direct injection of fuel into the cylinder of amixture-compressing internal combustion engine. The fuel injectiondevice includes a fuel injector, which is positioned in the cylinderwall at a distance to the cylinder head and across from the dischargeorifice, and an outlet opening, the jet axis of the fuel injector beingdirected to the region around the spark plug positioned in the cylinderhead. The fuel injector includes a magnet-activated valve needleprovided with helical grooves to generate a swirl flow of the injectionjet. The jet axis of the fuel injector is directed to the ignitionpoint-disposed in the center of the cylinder head.

Moreover, a device for the injection of fuel into the combustion chamberof a mixture-compressing internal combustion engine having externalignition is discussed in U.S. Pat. No. 5,941,207, in which the fuel isinjected, in the shape of a cone, into the combustion chamber at aspecific initial angle. The injected fuel fills up the combustionchamber in the shape of a cone, the effects of wall wetting beinglargely suppressed. During the compression phase, a piston having arelatively flat configuration deforms the injected fuel cloud into aspherical shape. The spherical mixture cloud mixes with the supplied airto a negligible degree at most and, while being compressed further, isguided to the spark gap of the spark plug.

German Published Patent Application No. 198 27 219 discusses a fuelinjector for an internal combustion engine that includes a disk foradjusting the fuel jet. It is provided with first nozzle orificesconfigured along a first circle, which is positioned coaxially to acenter axis of the valve body. Moreover, second nozzle orifices areprovided, which are disposed along a second circle which is positionedcoaxially to the center axis and has a larger diameter than that of thefirst circle. Each hole axis of the second nozzle orifices forms anacute angle with a reference plane that is perpendicular to the centeraxis of the valve body. The acute angle is smaller than that which isformed by each hole axis of the first nozzle orifices with the referenceplane. Therefore, fuel atomizations, which are injected through thefirst nozzle orifices, may be directed away from the fuel atomizationsthat are injected through the second nozzle orifices. As a result, thefuel atomizations, injected through the various circles of nozzleorifices, do not interfere with one another.

The methods or devices for the injection of fuel into the combustionchamber of a mixture-compressing internal combustion engine havingexternal ignition discussed in the aforementioned printed publications,are the complicated combustion-chamber geometries that are required inorder to mix the injected fuel with the supplied air, to form anignitable fuel/air mixture and to convey it for ignition to the vicinityof the spark gap of the spark plug. On the one hand, suchcombustion-chamber geometries are difficult to produce, and, on theother hand, it is impossible to optimize the combustion with regard tothe nitrogen-oxide emission and fuel consumption.

Moreover, in most cases, the spark plug is directly exposed to the fuelof the fuel injector. This not only exposes the spark plug to heavythermal shock loads, but also results in carbon deposits on the sparkplug electrodes, thereby considerably limiting the service life of thespark plug. The fuel injector discussed in German Published PatentApplication No. 198 27 219 provides that the fuel, injected into thecombustion chamber at different injection angles, for the most part,hits the walls of the combustion chamber or the piston, where it cools.For that reason, its combustion is associated with high pollutantemission or the development of soot.

SUMMARY OF THE INVENTION

The fuel injection system according to the present invention providesthat, due to the special configuration of the fuel injector relative tothe combustion chamber, the injection jet is guided in such a mannerthat the mixture cloud fills up the combustion chamber in an optimalmanner.

This may prevent the wetting of the combustion-chamber walls, may allowa low-emission and low-consumption combustion process.

The configuration of the spray-orifice plate of the fuel injector, whichproduces a mixture cloud that is able to optimally fill up thecombustion chamber.

The disk-shaped configuration of the spray-orifice plate is easy toproduce and is able to be installed in standard fuel injectors.

A plurality of rows of injection orifices is arranged on thespray-orifice disk, to provide a raster configuration that may beadapted as needed.

The choice of different diameters of the injection orifices providesthat, on the one hand, the jet pattern is able to be formed in thismanner and, on the other hand, the stoichiometry of the mixture cloud isable to be influenced.

The positioning of the fuel injector relative to the spark plug has theresult that the spark plug is not directly exposed to the fuel jet,since the injection jet moves tangentially to the spark plug, therebyextending its service life.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a longitudinal section through an example embodiment of thefuel injection system according to the present invention.

FIG. 2 shows a section through a mixture cloud generated in thecombustion chamber by a fuel injection system according to the presentinvention.

FIG. 3 shows a plan view of a first example embodiment of aspray-orifice plate of a fuel injector for a fuel injection systemaccording to the present invention.

FIG. 4 shows a plan view of a second example embodiment of aspray-orifice plate.

FIG. 5 shows a plan view of a third example embodiment of aspray-orifice disk.

DETAILED DESCRIPTION

FIG. 1, in a part-sectional schematized view, shows a first exampleembodiment of a fuel injection system 1, configured according to thepresent invention, for a mixture-compressing internal combustion enginehaving external ignition.

Fuel injection system 1 includes a combustion chamber 2, which isbounded by cylinder walls 3, a cylinder head 4 which includes ridgeslopes 5, and a piston 6. A spark plug 7 is positioned, for example, tocentrally project into combustion chamber 2. An intake valve 8 and adischarge valve 9 are sketched at ridge slopes 5.

A fuel injector 10 is positioned between cylinder wall 3 and cylinderhead 4 in such a manner that fuel is injected into combustion chamber 2in a plurality of injection planes 11. Four injection planes 11 areprovided in the present example embodiment. Fuel injector 10 is tiltedat an angle β with respect to a plane 12 that runs perpendicularly to alongitudinal axis 26 of combustion chamber 2. Injection planes 11 areinjected into combustion chamber 2 at a constant angle α_(y) withrespect to one another. Injection planes 11 are made up of injectionjets 20, which form a jet pattern that is described in greater detail inFIG. 2. The outer form of the injected mixture cloud 25, or envelope 24,of all injection jets 20, thus assumes a cylindrical form, whichcorresponds approximately to the shape of combustion chamber 2.

FIG. 2, in a sectional view through combustion chamber 2, shows the jetpattern generated by the first example embodiment of a fuel injectionsystem 1, configured according to the present invention, as shown inFIG. 1. According to

FIG. 1, fuel injector 10 injects the fuel into combustion chamber 2 infour injection planes 11. In the present example embodiment, each of thefour injection planes 11 includes nine injection jets.

A combined view of FIGS. 1 and FIG. 2 reveals that, in the present firstexample embodiment, a total of thirty-six injection jets 20, which aredisposed in four injection planes 11, are injected into combustionchamber 2. Injection planes 11 have the constant angular distance α_(y),injection jets 20 of each injection plane 11 having an angular distanceα_(x). However, this is not constant, but decreases from the innerinjection jets towards the outside. The following table provides anoverview of the spacings of injection jets 20 and injection planes 11for the first example embodiment.

Injection jet −4 −3 −2 −1 0 1 2 3 4 Injection plane a α_(x) −50° −39°−27° −14° 0° 14° 27° 39° 50° α_(y) 9° 9° 9° 9° 9° 9° 9° 9° 9° Injectionplane b α_(x) −50° −39° −27° −14° 0° 14° 27° 39° 50° α_(y) 0° 0° 0° 0°0° 0° 0° 0° 0° Injection plane c α_(x) −50° −39° −27° −14° 0° 14° 27°39° 50° α_(y) −9° −9° −9° −9° −9° −9° −9° −9° −9° Injection plane dα_(x) −50° −39° −27° −14° 0° 14° 27° 39° 50° α_(y) −18° −18° −18° −18°−18° −18° 18° −18° −18°

The injection planes are denoted consecutively from a through d; adenotes injection plane 11 which is closest to spark plug 7. The numbersfrom −4 through 4 denote the individual injection jets 20, symmetricallyto center axis 27 of mixture cloud 25. These configurations have beenentered in FIGS. 1 and 2.

FIG. 3 is a plan view of a first example embodiment of a spray-orificedisk 21 of fuel injector 10 of fuel injection system 1 configuredaccording to the present invention. Spray-orifice disk 21 shown in FIG.3 produces the jet pattern represented in FIGS. 1 and 2.

In the present example embodiment, thirty-six injection orifices 22 areconfigured on spray-orifice disk 21 in four injection planes 11. Nineinjection orifices 22 are configured in first injection plane 11 a, insecond injection plane 11 b, in third injection plane 11 c and in fourthinjection plane lid respectively. The configuration of spray orifices22, thus, corresponds approximately to a rectangular raster.

To completely fill up injection volume 23, which is a sub-space ofcombustion chamber 2, spray orifices 22 of injection planes 11 havedifferent diameters. The inner injection orifices 22 a of first andsecond injection plane 11 a and 11 b; have a larger diameter than outerinjection orifices 22 b of these planes. In contrast, the diameters ofinjection orifices 22 of third and fourth injection plane 11 c and 1 dare smaller. As a result of the different diameters of injectionorifices 22, injection jets 20 of the various injection planes 11penetrate combustion chamber 2 to different depths. Fuel injectedthrough inner injection orifices 22 a of first or second injection plane11 a or 11 b nearly reaches cylinder wall arranged diagonally acrossfrom fuel injector 10, whereas injector jets 20, injected throughinjection orifices 22 of third and fourth injection plane 11 c and 11 d,are more likely injected in the direction of piston 6 and, due to thesmaller diameter of injection orifices 22, cover smaller distances incombustion chamber 2.

Thus, the arrangement and nature of injection orifices 22 and injectionplanes 11 may be selected suck that combustion chamber 2 is nearlyentirely filled with injected fuel, without cylinder wall 3 or piston 6being wetted too much. As a result, the fuel consumption is reduced, andthe nitrogen oxide emissions decline as well.

Due to the configuration of injection orifices 22, their diameter, andthe horizontal and vertical angular distances of the individualinjection jets 20 to one another, spray-orifice disk 21 gives injectedmixture cloud 25 approximately to form of injection volume 23. Envelope24 of all injection jets 20 and injection planes 11, thus, is providedwith a cylindrical form, which corresponds approximately to the shape ofthe area of combustion chamber 2 left free by piston 6.

The numerical diameters of the individual injection orifices 22 may be100 μm, for instance, for inner injection orifices 22 a, while thediameter of the outer injection orifices 22 b or injection orifices 22of third and fourth injection planes 11 c and 11 d may be 25 μm, forinstance.

FIG. 4 shows a second example embodiment of a spray-orifice disk 21 offuel injector 10 of fuel injection system 1 configured according to thepresent invention. In contrast to spray-orifice disk 21 shown in FIG. 3,spray-orifice disk 21 of the present example embodiment includes onlythree injection orifices 22 each are positioned. This results in a totalnumber of twenty-four injection orifices 22. In a section through fuelinjection system 1, which corresponds to FIG. 1, three injection planes11 a, 11 b and 11 c would thus be available to fill up injection volume23.

Injection orifices 22, once again, have different diameters. In thepresent example embodiment, four inner injection orifices 22 a have adiameter of approximately 100 μm, whereas the injection orifices ofthird plane 11 c and outer injection orifices 22 b may have a diameterof 50 μm, for instance.

In the following table, the tilting angles of injection planes 11 andinjection jets 20 with respect to one another are listed for the secondexample embodiment.

Injection jet −4 −3 −2 −1 1 2 3 4 Injection plane a α_(x) −47° −35° −22°−8° 8° 22° 35° 47° α_(γ) 10° 10° 10° 10° 10° 10° 10° 10° Injection planeb α_(x) −47° −35° −22° −8° 8° 22° 35° 47° α_(γ) 0° 0° 0° 0° 0° 0° 0° 0°Injection plane c α_(x) −47° −35° −22° −8° 8° 22° 35° 47° α_(γ) −10°−10° −10° −10° −10° −10° −10° −10°

Injection plane a, once again is closest to spark plug 7.

FIG. 5 represents a third example embodiment of spray-orifice disk 21 offuel injector 10 of fuel injection system 1 according to the presentinvention. As in the first example embodiment, injection orifices 22 areconfigured in four injection planes 11. However, in the present exampleembodiment, there are only six injection orifices 22 per injection plane11. This results in a total number of twenty-four injection orifices 22on spray-orifice disk 21. Inner:injection orifices 22 a have a diameterof 100 μm, for instance, while outer injection orifices 22 b have adiameter of 50 μm. Injection orifices 22 of fourth injection plane 11 dare again the smallest.

In the following table, the tilting angles of injection planes 11 andinjection jets 20 with respect to one another are listed for the thirdexample embodiment.

Injection jet −3 −2 −1 1 2 3 Injection plane a α_(x) −44° −28° −10° 10°28° 44° α_(y) 20° 20° 20° 20° 20° 20° Injection plane b α_(x) −44° −28°−10° 10° 28° 44° α_(y) 10° 10° 10° 10° 10° 10° Injection plane c α_(x)−44° −28° −10° 10° 28° 44° α_(y) 0° 0° 0° 0° 0° 0° Injection plane dα_(x) −44° −28° −10° 10° 28° 44° α_(y) −10° −10° −10° −10° −10° −10°

In the present example embodiment as well, injection plane a is closestto spark plug 7.

The present invention is not limited to the example embodiments shownand is also able to be applied to spray-orifice disks having more orfewer injection planes, or more or fewer injection orifices, which mayeven have different orifice diameters.

What is claimed is:
 1. A fuel injection system for an internalcombustion engine, comprising: a combustion chamber that is bounded by acylinder wall; a piston that is guided in the cylinder wall; a fuelinjector including a spray-orifice disk containing a plurality ofinjection orifices through which a fuel is injected into the combustionchamber, diameters of the plurality of injection orifices being arrangedon the spray-orifice disk in such a manner that, at a point ofinjection, the fuel is distributed homogenously in an injection volumeof the combustion chamber bounded by the piston and the cylinder wall,and the plurality of injection orifices being arranged on thespray-orifice disk in a plurality of rows in a raster-typeconfiguration; and a spark plug that projects into the combustionchamber; wherein the fuel injector injects the fuel into the combustionchamber in at least two injection planes that are set apart from oneanother by an angle.
 2. The fuel injection system of claim 1, wherein:the at least two injection planes have a constant angular distance. 3.The fuel injection system of claim 2, wherein: a jet opening angle of anenvelope of a mixture cloud is between 50° and 100°.
 4. The fuelinjection system of claim 3, wherein: injection jets of the at least twoinjection planes, injected through the plurality of injection orificesinto the combustion chamber, have an angular distance that decreasesstarting from a center axis.
 5. The fuel injection system of claim 4,wherein: those of the plurality of injection orifices on an edge of atleast one of the at least two injection planes are smaller than those ofthe plurality of injection orifices on an inside of the at least one ofthe at least two injection planes.
 6. The fuel injection system of claim5, wherein: those of the plurality of injection orifices on the edge ofat least one of the at least two injection plane are larger than thoseof the plurality of injection orifices on an edge of a further injectionplane of the at least two injection planes.
 7. The fuel injection systemof claim 1, wherein: the fuel injector is tilted at an angle withrespect to a plane that is perpendicular to a longitudinal axis of thecombustion chamber.
 8. The fuel injection system of claim 7, wherein:the angle is between 35° and 55°.
 9. The fuel injection system of claim1, wherein the spray-orifice disk is configured in such a manner that anenvelope of an injected mixture cloud has a nearly cylindrical form.